"Some of you would be aware that I have been planning to step down now for almost three years but had felt compelled to stay and guide management," Lim wrote in a letter to the SingPost board.

Lim, who has been a SingPost director since 1998 and the chairman since 2003, will step down on May 10. Lim will also quit his position as a director in July.

"He has led us with not just his great intellect and business acumen, but also with his heart. It is difficult to think of SingPost without Lim Ho Kee," SingPost said in a statement.

However, the Business Times reported that Lim's resignation comes in the midst of controversy about the quality of corporate governance at the company.

"Ho Kee is just initiating the start, there will be more announcements coming," SingPost independent director Zulkifli bin Baharudin told the business daily.

In December the company revealed that it had failed to adequately disclose independent director Keith Tay's interest in a 2014 acquisition. Following this SingPost commissioned a corporate governance review.

Besides the row over governance, SingPost has been focusing on transforming itself into an e-commerce and logistics player.

"The bottom line is that our transition to e-commerce and logistics is not assured. It's fraught with risk, but it's something we have to manage and there's no guarantee we'll succeed," the spokesman said.